How to repair the battery of an electric screwdriver with your own
Features of construction
The number of sections in the battery of an electric screwdriver depends on the power of the device and the type of battery. In standard tools as a battery is connected in series from 4 to 16 cans. The more compact and powerful they are, the higher the cost. Accordingly, the lighter the battery, the easier and more convenient it is to work with a handheld electric device. Battery sections are connected to each other by contact plates. The upper parts of both are on the outside of the case are power terminals that receive the charging current from the charger. These contacts can also be used to measure the total capacity of the battery.
There can be several external contacts on the plate. up to 5 pieces. Most often this number is found on expensive tools powered from lithium batteries. In these, it is important to monitor the charging current of each bank. this function is performed by the corresponding board and the temperature sensor. The charger has to be matched in capacity, otherwise the balance of currents will be disturbed.
Eliminate the memory effect
Not always screwdriver battery recovery requires some radical actions. It often helps to restore the capacity of the battery by alternating between full charging (until the charging lamp goes out) and full discharging. This method is also called “rocking the battery”.
How to erase the memory effect of a battery
It is connected with the so-called “memory effect” and is characteristic of nickel batteries. And it is especially noticeable in nickel cadmium batteries. It occurs when a battery that has been discharged to zero is not fully charged and starts to run or vice versa. This leads to a enlargement of the active substance crystals which reduces the active surface area.
Follow the manufacturer’s recommendations for charging and discharging.
The so-called “training” of the battery helps to eliminate this effect or reduce it considerably. It consists of repeating the full charge and discharge cycles.
To do this, the battery to be regenerated is discharged completely using, for example, a light bulb. Then it is fully charged and discharged again. Repeat the process 5 times and if the individual elements of the battery are intact, the characteristics will return to normal or close to it.
Excitation of the battery
The method is suitable for all types of batteries. Necessary:
- Disassemble the battery.
- Use a multimeter to find dead batteries.
- Excite them by means of pulse discharge. This will work for: 12 volt battery, power supply, spot weld, etc.д. The pulse should be short-lived and does not need to be repeated many times. It is enough to excite the battery to be seen by the charger.
- Put all the elements back together (if they have been disassembled) and place them in the battery case.
This method is not perfect, because after some time (from a week to a month) the battery voltage will fall again. It is especially suitable for nickel-cadmium batteries.
Being able to work with a tool such as an electric screwdriver without plugging it in is convenient, practical and, most importantly, necessary. After all, you often have to perform any work in places where it is almost impossible to reach the mains cable. Construction tool stores offer a wide range of screwdrivers, including Bosch, as well as the popular Hitachi and Makita. But unfortunately the battery life of any drill or similar tool is short. 5 years maximum. It happens that the battery of an electric screwdriver is no longer charged, and after a shorter period of time. Buying a new battery in a hurry is not profitable. For the same amount of money you can buy a new electric screwdriver. Therefore, it is worth trying such an option as the restoration of the electric screwdriver battery with their own hands.
How to repair the battery of an electric screwdriver
The use of DC power supplies has made it possible to create a compact and mobile tool. As the battery capacity decreases and the operating characteristics of the equipment, the owner faces the question of how to restore the battery of an electric screwdriver. The algorithm depends on the type of battery, some products are not repairable and are replaced with new devices.
What you need to know before you start rebuilding a screwdriver battery?
Most batteries in power tools have the same design features (compact cells connected in series). 2. Pay attention to battery type (Ni-Cd, Ni-MH, and Li-Ion) and capacity (in mAh). 3. When disassembling the battery pack, the polarity (/-) of the connections must be monitored. 4. The “banks” are protected from overheating by a thermal fuse. 5. To recharge a Li-Ion battery at home is very difficult. the appropriate experience and skills are required (see below for how to determine if it is working).
Screwdriver battery renewal service is professionally provided by Neovolt (click here for help).
Electric screwdriver battery malfunction detection and recovery
Before you begin to repair the battery, you should determine its fault, otherwise the repair will be quite difficult or completely impossible. It should be noted that the failure of all battery cells at the same time is impossible, except in rare cases where there may have been a prolonged short circuit of the battery output terminals.
To determine the malfunction should:
- put the battery on charge and wait until it is fully charged.
- After that disassemble the case, and measure the voltage of each charging element. The voltage difference across the banks for nickel cadmium batteries may be in the range of 1.2-1.4 V, and the difference for lithium batteries may be about 3.8 V.
- Banks with less than the nominal voltage should be marked. After that, the battery should be reassembled and given a full load until a noticeable discharge.
- Then disassemble the battery again and measure the voltage of each bank.
- Usually the biggest voltage sag will be in the marked cells, which will need to be “resuscitated” or simply replaced.
If the electric screwdriver requires 12 V voltage to work, you can try to find the faulty elements in a simpler way. To do this, you need:
- Produce a full charge of the battery, then disassemble it and measure the voltage of each cell.
- Then use a 12 volt light bulb to fully discharge it and measure the voltage of all the cells again to determine which ones are faulty.
Instead of a light bulb, you can use a resistor that matches the voltage.
Repair and replacement of electric screwdriver battery cells
The most effective method of how to restore the battery of an electric screwdriver is to simply replace the failed charging cells that were found during their inspection.
To make repairs, you will need a donor, that is, a second battery, which also has failed banks, if there is no such, you can buy new cells online. Today there are enough online stores that are ready to deliver new batteries directly to your home by courier service.
Important. Purchased elements should have the same capacity and dimensions as the cells to be replaced.
For the repair you will need to prepare: a soldering iron, tin solder and alcohol flux (preferably).
The very process of replacing the charging elements does not provide any complexity, if you have a skill in soldering.
Rebuilding an electric screwdriver battery
Warning. In order not to damage the battery when working with a soldering iron, soldering must be done quickly.
Repacking Makita 18v Lithium battery with New Cells (Save ‘s)
It is recommended that native plates be used to connect the cells, and if they cannot be used, replace them completely with the same size, but made of copper. This is needed for the proper charging process. With different cross sections of the connecting plates between the elements, they will heat up, and of course, to protect the charging jars will constantly actuate a thermistor.
Care must be taken when assembling the batteries. The connection should be sequential. the minus of each battery is connected to the plus of the next element.
After all the elements are completely assembled, their potentials are adjusted, since they will be different for the time being. To do this, it is necessary to conduct a certain charge/discharge cycle. The repaired battery is fully charged and then allowed to stand for approximately one day. After one day the individual voltages of all cells should be measured and if the assembly has been correctly done, the voltage of each cell should be equal to 1.2 V.
After that, the battery must be fully discharged again. To do this, the assembled battery, using an electric screwdriver, is given a full maximum load until it is completely discharged. The main thing is not to overload the electric screwdriver itself, so it does not have to be repaired in the future. This charging/discharging procedure must be repeated several times in a row.
In the same way, about every three months, it is recommended to carry out a procedure to erase the “memory effect”, which will prolong the battery and the electric screwdriver itself.
How to recover a DeWALT lithium battery from a DeWALT cordless screwdriver?
Lithium batteries are increasingly being used in the home. Nowadays they are more and more common as replaceable batteries for screwdrivers and other power tools. Despite their advantages, lithium batteries are not without disadvantages.
For example, after 1.5 years of use, the batteries in a DeWALT impact wrench quickly ran out of power and were no longer able to work. Batteries were charged to a maximum of 14.4 volts, even though I used the standard DCB-107 battery charger for this. In addition, charging was very fast, instead of 60 minutes, at most 15 minutes.
Before to tell how I solved this problem I would like to introduce the reader about the device of a lithium battery for a screwdriver.
This is what the original DeWALT DCB-145 battery pack looks like.
To open such a battery you need a TORX type hex screwdriver. The rechargeable battery consists of 4 lithium (Li-ion) “cans” Samsung SDI INR18650-13B capacity of 1300 mA / h each. All four “banks” are installed in a plastic box and connected in series with conductive plates. Plates are welded to the battery terminals by spot welding. You can see that it is a quality factory assembly.
I would not advise to separate the “banks” of a composite battery by making a cut in the connecting current-carrying plates. I did so and regretted it. Below I will tell you why you should not do this.
Samsung SDI INR18650-13B batteries themselves do not have a built-in charge/discharge controller. Unfortunately, I could not find the documentation for this particular battery model (index 13B). But, judging by the parameters of the batteries of this line, the maximum continuous discharge current (Max Continuous Discharge Current) can be from 18 (INR18650-13L) to 23 (INR18650-13M) amperes! No wonder they don’t have a controller built in.
There is also a 5 pin connector and a small printed circuit board.
A multi-pin connector is required so that each of the four INR18650-13B batteries can be monitored separately while charging. As you know, the voltage over 4.1
4.2V is dangerous for lithium batteries and can damage or even cause a fire. Therefore, the charger equalizes (balances) the current through each “bank” of the composite battery so that the voltage at each bank does not exceed 4.1V.
Also on the printed circuit board is a temperature sensor, which is attached to one of the lithium “banks.
Thanks to a sensor, the DeWALT DCB-107 regular charger measures the temperature of the battery and shuts down charging if the battery is overheated or under 4C. There is some circuitry besides the temperature sensor, but it is sealed.
Such a battery pack is called a “Pack for Power Tool”, that is, a “Pack” or battery pack for power tools. This is what it looks like.
Large companies like Samsung supply such assemblies to power tool manufacturers on request. Perhaps that’s why I failed to find the exact specifications for INR18650-13B batteries.
With the device of the Li-ion batteries for power tools, we got acquainted. Back to our “dead” batteries.
Before the batteries “died” they were very strongly discharged. We used the cordless screwdriver until the battery was empty, and then, after taking a break, we worked with it for a while longer. After that the batteries didn’t charge well and didn’t hold capacity.
How to Repair Electric Screwdriver
After measuring the voltage of each “bank” of the battery, it turned out that 3 “banks” of 4 batteries are not fully charged. to 3.5 volts. Only one battery was charged to the necessary 4.1 volts (for Li-ion).
If you add up the voltages of all the batteries, we get exactly the same 14.4V. Let me remind you that the regular charger charged the battery very quickly and disconnected.
The first thing that came to mind was to replace those lithium “cans” that were not fully charged. But, the search for the original INR18650-13B yielded no results. Perhaps due to the fact that such assemblies are available only on order and do not retail. And the cost of four new batteries, for example, INR18650-22R was almost equal to the price of one DeWALT DCB-145 battery. So I decided at that time to refuse to replace the batteries.
And, here a reasonable idea came to mind, but it is, as always, lagging behind. What if the OEM charger failed to properly balance a composite lithium battery after a deep discharge? That is, regular DeWALT’s charger charged one “bank” to necessary 4.1V and shut down. At the same time, the remaining 3 lithium “banks” were not fully charged, but only to 3.5V.
I decided to check the DCB-107 Battery Pack to see if it was faulty in any way, but it turned out to be fine. And the charger charged the new batteries just fine.
So, I came to the conclusion that the regular charger failed to properly balance the composite lithium battery after a deep discharge.
It was decided to discharge/charge each lithium 18650 bank separately using a third party charger. For this I used a Turnigy Accucell 6 charger (similar to IMAX B6), which I told you about before.
How to Repair a weak Drill / Screwdriver / Battery runs out quickly
I discharged each 18650 to 3V with 0.3A. Then I charged them to 4.1V with 0.5A. Then discharged again in order to determine how much current was being poured into each particular “bank”. This is necessary in order to evaluate their capacity. As it turned out, the batteries are serviceable and each of them was “filled” from 1164 to 1186 mA. Which is not so far from the claimed capacity of 1300 mA/h. So I made sure the batteries were in good order and it was not necessary to replace them.
After the test (charge-discharge) of each battery, we measure the voltage at each lithium “bank”. It should be within 3.1
3.3V each. This way the composite battery will be discharged to 12.4
Then I assembled all the jars in the box, soldered the board with the connector and installed it in the case. I put the fully discharged DeWALT DCB-145 battery pack into the original DeWALT charger and measured the charging time. As I expected, after 1 hour (60 minutes, as the manual says) the charging was finished.
As a “control shot”, I measured voltage on B and B terminals-. It was 16.4V, as it should be for a fully charged battery.
So I was able to restore the two batteries DeWALT DCB-145 and avoid wasting money on buying new batteries, the total cost of which is almost equal to the cost of an inexpensive screwdriver.
Now about the rake that I’ve stepped on.
Warning! Assembly must be done very carefully and avoid short circuits between the “can” leads and those leads that go to the balancing connector. If you short-circuit something with pliers or tweezers, there will be fireworks of sparks! I learned that the hard way. The currents are such that 0.5 mm wire. they melt like the thinnest wire in a fuse.
Also I strongly advise against dividing the lithium batteries by cutting or biting through the connecting current carrying plates that are welded together.
First of all, this is not necessary. Charge each “bank” by simply connecting the charger terminals to the poles of the desired battery. The only thing that may be necessary is to unsolder the pins of the balancing connector and temporarily remove the connector itself from the assembly.
Secondly, you can damage the lithium batteries insulation and therefore short-circuit them.
Third, after the lithium “cans” are tested, there is the question of connecting them together. And even if you manage to solder the plates together, putting such an assembly back into the case will be quite a laborious task. The battery case is very tightly fitted to the dimensions of the assembly.
Where to buy lithium batteries to replace defective ones?
And finally I will touch on the topic of lithium battery replacement. If it happens that the batteries in your screwdriver has become worthless and you need to replace them, then at the moment it is not difficult to find a decent replacement. For example, on AliExpress you can find lithium batteries from Samsung, LG, Sanyo, Panasonic, Sony.
To upgrade my 12V screwdriver with nickel-cadmium battery, I bought the Samsung INR18650-25RM batteries.
I bought them at the well-known and trusted LiitoKala store. Apparently, the batteries are original. Anyway, I did not notice any difference in weight, capacity and workmanship. The seller insists that the batteries are original, but they apparently have no right to “light up” the Samsung brand. That’s why all batteries are marked with a Samsung branded store sticker.
The rework was a success. I didn’t bother with protection and charge cards, I just brought out the power wires and the wires for the balancing connector. I charge everything directly from a Turnigy Accucell 6 universal charger. I just had to do it quickly, because the summer was coming to an end.
To replace nickel batteries (NiCd, NiMh) with lithium it is better to take those with welded-on “petals”. This will make it easier to solder the composite battery.
It is worth noting that the batteries INR18650-25RM just used in those very Pack for Power Tool. Before buying it, I advise you to google the datasheet for the battery (eg: “Samsung inr18650-25rm datasheet”). It says everything you need to know: typical charge and discharge currents, purpose (tools, toys), graphs of capacity loss after a few cycles and much more.
Easy rebuild: replacing a few elements
If operations with distilled water and “reflashing” nickel-cadmium batteries require time and skill, the replacement of spent cells requires only a multimeter, a soldering iron and new battery banks.
Before replacing the battery, it is necessary to diagnose the battery and the correct way to do this is described above. The battery consists of individual cells which have to be soldered out. Use low-power soldering irons for soldering, otherwise the high temperature can damage the power supplies. Low voltage cells should be set aside or marked.
Tip! If possible, it is better to use a soldering station with power control or spot welding.
After identifying the faulty power sources, they must simply be replaced with new ones, which are re-soldered into the total battery. The cost of individual cans is much lower than the entire assembly, so savings will be apparent. After all cells are assembled in the battery, it is necessary to charge/discharge the battery several times.
Electric screwdriver malfunctions
Despite the variety of power sources for batteries, they all have a similar structure, which means that their faults are the same:
- breaking of the chain connecting the banks;
- loss of charge capacity (one or more);
- Evaporation of electrolyte;
- Lithium decomposition (only in some batteries).
Battery cell capacity loss is a common problem that occurs even when using the device for a short period of time. The defect is caused by the fact that even when a single charge loses capacity, the remaining banks can no longer be fully charged. The result is a reduction in the continuous use of an electric screwdriver.
This type of failure is caused by the “memory effect” or the evaporation of electrolyte in the cells, which occurs when they are strongly heated. Nevertheless, even with such troubles you can cope at home, without resorting to professionals.
cells are repaired or replaced with new ones. The second case is relevant for lithium-ion batteries, in which the lithium has decomposed. in this case you will only have to buy a new power source.